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Laser Anemometer Measures Flow in a Centrifugal Compressor

High-resolution data are representative of flows in practical centrifugal compressors. Detailed measurements of complex flow fields within the NASA Low Speed Centrifugal Compressor (LSCC) have been acquired. The measurement data provide insight into the fundamental physics of flow in centrifugal compressors, and can be used to assess computational fluid dynamics codes and to develop flow-physics models. The resultant benefit is better predictive computational tools and shorter design cycle times.

Posted in: Mechanical Components, Briefs

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Portable Airborne Multispectral-Imaging System

This system can be put into operation almost anywhere on short notice. A portable instrumentation system that includes an airborne and a ground-based subsystem acquires multispectral image data over swaths of terrain ranging in width from about 1/2 to 1 km. The system was developed especially for use in surveying coastal environments; it is also well suited for performing remote sensing in connection with agriculture, aquaculture, forestry, environmental decontamination, and general environmental monitoring. The system can be stowed in two suitcase-size containers that can be transported as check-in luggage on a commercial airline. Once the system has been delivered to its destination and unstowed, the airborne subsystem can be launched over unprepared terrain and controlled from the ground-based subsystem, which can be operated from a minivan or a similarly sized vehicle.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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High-Altitude Flight Test of the Perseus B Airplane

Flawless aerodynamic, propulsion, and control performance was observed. The Perseus B remotely piloted vehicle (RPV) has achieved a record altitude for a single-engine, propeller-driven airplane of 60,260 ft (18,367 m) on June 27, 1998. The Perseus B is one of the test-bed aircraft developed under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program for use in conducting high-altitude, long-duration missions carrying atmospheric sampling and sensing payloads for the scientific community within NASA and other agencies.

Posted in: Mechanical Components, Briefs

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Filled Skutterudites as Thermoelectric Materials

The highest known thermoelectric figure of merit was observed in one of these materials. Filled skutterudites have shown promise as semiconducting materials with superior thermoelectric properties at temperatures up to at least 650 °C. This finding is a breakthrough in a continuing investigation of the potential utility of skutterudites as thermoelectric materials. Previous results of this investigation were reported in several articles in NASA Tech Briefs; namely, "Skutterudite Compounds for Power Semiconductor Devices" (NPO-19378), NASA Tech Briefs, Vol. 20, No. 3 (March 1996), page 60; "Two Potentially Useful Ternary Skutterudite Compounds" (NPO-19409), NASA Tech Briefs, Vol. 20, No. 11 (November 1996), page 66; and "Preparation and Some Properties of n-Type IrxCo1 — xSb3" (NPO-19852), NASA Tech Briefs, Vol. 20, No. 11 (November 1996), page 94.

Posted in: Materials, Briefs

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Camera Images Hydrogen Fires in Three Wavelength Bands

The camera filters and processing can be customized for other multispectral imaging applications. A special-purpose multispectral video camera has been designed to provide an enhanced capability for viewing hydrogen fires. Hydrogen fires do not emit sufficient visible light to be seen by the unaided human eye, but they do emit strongly at other wavelengths — especially in the infrared and near-infrared portions of the spectrum. Therefore, like some other video cameras developed previously for the same purpose, this camera is designed to respond to infrared light emitted by hot water molecules in hydrogen flames. Going beyond previous designs, this camera provides a combination of imaging in three wavelength bands and processing of the three images, all for the purposes of (1) reducing spurious responses to background light and solar radiation, and (2) synthesizing an image of a hydrogen flame overlaid on an ordinary visible-light image of the scene that contains the flame.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Instrument Measures Fluorescence From Chlorophyll in Plants

Effective discrimination against solar background radiation is achieved without critical optical and mechanical parts. An optoelectronic instrument, known as a plant fluorescence sensor, is being developed for use as a working tool in agricultural settings. This instrument is a remote, passive monitor that provides a means of discerning plant stress at very early stages. With sufficient warning, the user could provide timely applications of fertilizer, water, and/or pesticide to achieve maximum crop yield at minimum cost. Figure 1 presents two views of the plant fluorescence sensor. The instrument is the subject of U. S. Patent 5,567,947.

Posted in: Test & Measurement, Briefs

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Initialized Fractional Calculus

Initialization functions are essential to a revised formulation suitable for engineering and scientific applications. The fractional calculus (which admits of integrals and derivatives of non-integer order) dates back almost to the origin of the better-known ordinary (integer-order) calculus, but thus far has been treated more as a mathematical curiosity than as a scientific and engineering tool. Increasingly many physical processes are found to be best described using fractional differential equations. These processes include: viscoelasticity, rheology, electrochemistry, fractal processes, and many diffusion processes. The application of the fractional calculus to scientific and engineering problems has been inhibited by difficulties that arise from the basic definitions given heretofore for integrals and derivatives of arbitrary order. These difficulties are associated with the initialization problem, which is explained below.

Posted in: Information Sciences, Briefs

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